Fermentation temperature is maintained to keep yeast happy. It has little to do with beer color. For example, you may have a dark lager like a Bock beer that requires lagering at low temperatures with a lager yeast. Or you may be brewing a light pale ale that requires a higher temperature while using an ale yeast. The yeast company should provide you with ideal temperatures to maintain while using a particular strain of yeast. Try to use only high quality liquid yeast cultures.

What about if the temperature drops? We have wood heat, and no matter how hard I beat my roommates to keep a fire lit it wouldn't happen to save their lives, so, while I sleep the temp might get down to 58-60'F, then rise back to 75 or so mid-day. Is this -bad- or is it just slowing down fermentation or carbonation? I'm having problems carbonating the darn stuff, in particular with an amber wheat and a chocolate malt porter.

I'm fairly new to homebrewing and I've been reading some conflicting theories on secondary fermentation and lagering. I want to make a German/Euro style pilsner and I'm using cool lager yeast. Some books suggest 2-4 weeks lagering (after bottling) at close to 0 degreees (Celsius) while others mention putting the bottles in a warm place after bottling to kick off the secondary fermentation. Which is the better approach (or is there a good combination) to achieve a clean crisp pilsner style?